The interactions between CO2 and various surface functional groups and terminations in activated carbon were examined using high-accuracy ab-initio methods.We showed that the adsorption of CO2 comprises 2 different sets of Lewis acid (LA)–Lewis base (LB) interactions: the C(CO2) as LA with the charge abundant edge atoms/groups as LB and the charge deficient edge atoms/groups as LA with O(CO2) as LB.The preferable adsorption structures and energies correlate well with the shape and the intensity of the electrostatic potential surface of the absorbent.The K+ ions that reside after activation of carbon with KOH,play a key role in promoting CO2 adsorption.In addition,HCl molecules anchored in N-doped carbon have a similar promotion effect on CO2 adsorption,which contradicts the conventional wisdom that the neutralization of basic sites by acids diminishes the adsorption of acidic CO2 gas.These findings the way for design and preparation of novel microporous carbon material for selective CO2 capture.